23 OutlinesUse the alpha-shapes, which are slightly larger than the normal shapes, to create the outline, a flange of dark pixels slightly behind the billboard.The outline of these flange pixels is opaque because alpha is one, colored black because the C is black, and farther from the camera than the particle itself because d is zero.

28 Cel-Shading PassWith ambient light color Ka, light color Kl, camera-space direction L to the light source, and diffuse color C from the texture map, the pixel at (x, y) is colored by a pixel shader using the following equation:yN · L

29 Shadow Volumes Compute the silhouette of the casterExtrude this to form a polyhedron bounding the volume of shadowed spaceShadows are intersection between the volume and the scene

30 Billboard Shadows Caster is perpendicular to viewer and lightVolume is a rectangular prismFour sides are parallel to the view vectorOnly 3 polygons to be rendered: one billboard and two shadow faces

31 Nailboard ShadowsApply the depth displacement to the shadow volume as well as the billboardShadow volume visualization